PS In reworking this puzzle I noticed that the first "5-star constellation" I found was not really necessary -- there was a triplet {7, 8, 9} that would have served the same purpose, if I had only noticed it.

I found that early on there is a coloring on <7> which excludes that value from R9C3. This is a big help. Then, the puzzle can be solved via an X-wing on <3> (which also appears early), and the last step is an XY-wing on <9>. (After that, all moves are forced.)